Blasting explosive



Patented, Dec. 19, 1944 2 ,365, 70

UNITED STATE-S PATENT OFFICE 2,365,170 I r r g BLASTINGEXPLOSIVEporation oi Delaware No Drawing. Application April 13, 1940, Serial No.329,492

11 Claims. (01. 52-13) 'l 'his invention relates to gelatin dynamites ofI improved explosive properties and more particularly to gelatindynamites in which the improvement' results ,from the incorporationtherein of fairly well established that this results because theapparent density of the gelatin has increased, approaching thetheoretical density of the uni..- ture of ingredients used.

"*plish this without seriously departing from the basic characteristicsof gelatin dynamites, which involve in addition to water resistance,high density and plasticity. A still further object of low density,cellular, carbonaceous ingredients 5 this invention is to provide a lowdensity, celluwhich have been specially treated to provide lar,carbonaceous ingredient, which when incorstiiiened cell walls. poratedin a gelatin dynamite, will prevent ex- For use in blasting under wetconditions, or' I cessivecompression under high pressures. Still atvarious depths under liquid heads such as, for further objects willappear hereinafter. example, water and oil, blasting gelatin and Theobjects of this invention are accomplished gelatin dynamites have longbeen used. As is in accordance with this invention by using low wellknown in the art, gelatin dynamites condensity, cellular, carbonaceousingredients, sist of a plastic explosive formed by the gelatintreatedwith a material which will effectively ization of nitroglycerin withnitrocellulose to stifien the ingredient so that the cell structurewhich mixtures may be added oxidizing salts and 15 will not be destroyedunder high liqui D carbonaceous ingredients. These compositions sures,as an ingredient in gelatin dynamite. are especially resistant to thepenetration of water We shall within this specification and claims andfor that reason are particularly useful for use the term gelatindynamite to include the blasting under liquid heads. three main classesof gelatin dynamites which are Difiiculties have been encountered in thepast commonly known as straight gelatins, ammonia with gelatin dynamitesbecoming insensitive after gelatins, and permissible gelatins. Thestraight prolonged storage and when used under the great gelatlns range.in stren th, ac d t the sual depths of water and oil'such'as areencountered, terminolo y. fr m to 100%. The latter is for example, inseismographic prospecting and oil commonly know as blasting atin. Thesewell shooting. In the latter case, it has been 29 ordina y contain aelatini ed liquid e plos ve ingredient, with varying proportions ofsodium nitrate and combustibles, depending on the strength and otherproperties which may be required. The ammonia gelatinsusually contain aThis dimculty has been overcom to a, certain 30 smaller lii'OPOl'tlOnDfgelatinized liquid explosive extent by the incorporation of suitable lowdensity: ingredients in the gelatin dynamite. However, when such gelatindynamites are used under the highheads of liquid that are prevalent inoil well shooting and -seismographic prospectof explosive compositionsof improved sensitive- -ness under adverse conditions. A further objectof this invention is the preparation of gelatin dynamites which willfunction successfully after more or less prolonged subjectiontoimmersion under great depths of water or other liquids. A stillfurther objector this invention is toaccomthan straight gelatins oi thesame grade strength, the strength being made' up by the use of ammoniumnitrate. Permissible gelatins may be of g either the straight or theammonia type. with the addition of a safety ingredient which permitstheir safe use in coal, mines, where there is danger of explosion frommine gas and coal dust.

We have found that the low density, carbonaceous ingredients, preparedin accordance with the 'copending application of Lawrence Serial No.326,654, produce a gelatin which will suffer less than the usual degreeof compression under high pressures. carbonaceous ingredients which aresuitable for this purpose include ground cork,

balsa, bagasse, bongo wood, hemp hurds and their equivalents. Thetreatment to which they are subjected involves impregnation of theingredients .to eiiect a stiffening oi the cell walls with aheat-hardening synthetic resin such as the urea-aldehyde,phenol-aldehyde, thioureaaldehyde type resin and the like, andsubstantially heat-hardening in situ: The synthetic resins may be formedand hardened on and in the carbonaceous ingredient or applied as anintermediate condensation product, from a solution high liquid pressuresand the density is often lower than is desirable. By using treatedcarbonaceousingredients, a considerably greater improvement insensitiveness under high liquid pressure is secured with a smallquantity of low density material and at thesanie time gelatins of thedesiredhigh density are produced. 'I'hus,

by the prior art gelatine 'dynamites can-be prepared which will have adensity of 1.3 g./cc. or less and will shoot after 2 hours under 120lbs.

- per sq. in. (275 it.) of water by incorporation of 4% of ordinaryground cork. However, incorporation of 2-3% of treated cork will givegelatins having a density of 1.4 g./cc. or more which will shoot after 2hours under at least 250- lbs/sq. in. (580 ft.) oi. water. i

Our invention makes it possible to prepare gelatin dynamiteseconomically and simply which are of greatly increased effectivenesswhen" used under igh presgurgs J 'Weareaware that it has been proposedto use .low density carbonaceous ingredients, which have beenimpregnated'with materials to reduce their nated materials whenincorporated in gelatin dynamites do not effectively improve theirsensitiveness under high pressures. It is to be noted that thecarbonaceous materials treated to give stiffened cell walls havesubstantially the same absorbency for nitroglycerin before and aftertreatment, and in some cases there is a material increase in absorbency.

In order to show that the absorbency of treated carbonaceous material issubstantially constant or increased, the following table is given:

absorbency for nitroglycerin. These impreg-' aseairo ever, essential, assamples of cork with the :tob-

lowing screen analyses have given good results.

Screen test A B C D E Per cent Per cent Per car Per cent Per cent On 12mesh 0.6 Nil 1. 0 Nil Nil On 20 mesh 58. 5 42. 0 79, 6 1 Nil On 30 mesh22. 5 50. 0 l5. 5 100 On40mesh 17.5 6.0 3.0 .s Through 40 mesin 1. 0 2.0 l. G

The treatment may be carried out in the following manner. The cork isplaced in a suitable container and a solution of urea in an acqueousformaldehyde solution is added to the cork and the mixture thoroughlyincorporated. The mixture is then heated tocause condensation of theurea-formaldehyde resin and to dry the cork. This drying mayconveniently be carried out at about IO-190 C; The impregnated cork andresin are then heated to harden the resin. This may be done by heatingfor to 1 hour or more at 100 C. or for shorter periods at temperaturesup to 150 C. This procedure, as will be obvious to those skilled in theart, may be varied considerably.

Alternatively the urea -iormaldehyde solution may be sprayed on the hotcork and the mixture dried and the resin hardened as before, or the ureamay be mixed with the cork and then the formaldehyde solution, added anddrying and hardening of the resin carried out as before.

The ratio of urea to formaldehyde may be varied over wide limits, forexample, from 1 part of urea and 2 parts of 40% formalin (37%formaldehyde by weight) to 1 part of urea and 5 parts of t0% formalin,although we do not wish to be limited by these proportions. Furthermore,the solutions may be diluted to any desired degree, although for economyof operation, it is desirable to use quite concentrated solutions.

Instead of preparing the resin in above de-- scribed manners, a partialcondensation product of urea and formaldehyde may be prepared by methodswell known in the art which can be applied from an aqpeoussbl'flion' or"from solution in an Manic solvent such as ethyl alcohol, the

. carloonaceous material treated, the solvent evaporated, and the resinheat-hardened.

In treating cork with urea-formaldehyde solution, good results have beenobtained when the quantity used was such as to give a final productTABLE I Per cent absorbency Absorbency factor Ingredient R i R i cs 11cs 11 Plain treated Plain treated Cork 37.1 45.0 59 a2 Balsa 76. 2 76. 0320 317 Bagasse-Celotex. 78. 0 76. 0 355 317 Bagasse-Godchaux 68. 0 65.4 212 189 containing from about 15% to about 45% oi resin. The preferredrange is from about 30% to about 40% resin. by weight'of the finaltreated cork.

Other carbonaceous ingredients such as balsa, bongo wood, or bagasse maybe used, but when these types of materials are used, it is found that alower percentage of resin will give results which areas effective ashigher percentages with ground cork. Thus, for examplawith treatedbalsa, it is preferable to have about 25% to about 35% ofurea-formaldehyde resin ,by weight of the final product. Thisurea-formaldehyde resin treated balsa orits equivalent may be used inexplosive compositions in the same manner that the ureaiormaldehyderesin treated cork is used to ob-' tain explosives with approximatelythe same properties.v

In the use of the phenol-aldehyde resins to treat cork, the mostsatisfactory results are obtained when the resin is formed in and on thecork cells. For example, cresol may be dissolved in 37% formaldehydesolution, catalyst stirred in and the mixture added to the cork, Byheating A treating are the following:

the mixture of the cork with the cresol and form.-

aldehyde, condensation, drying and hardening of the resin areaccomplished. The final hardening operation can be carried out attemperatures in the range of -100-150 c,

Other heat-hardening resins or combinations may be used to treat thecellular material, for

concentrated solution of these materials in an I organic solvent. Thishas the advantage of limiting the quantity of solvent used, thus reduceing the fire hazard and eliminating the necessity of installing arecovery system for the solvent.

The carbonaceous ingredients such as cork,

balsa, bagasse, etc., treated with a suitable heathardening resin haveahard, rather gritty feel in contrast to the soft and compressiblequalities ofthe untreated material. Incorporation of these ingredientsin gelatin dynamites tothe extent of about 2-3% results in greatlyimproved ability to detonate under conditions of high water pressure.

In the preparation of the specially treated carbonaceous material, twofactors are of especial importance: Mixing with the resin ingredients ina relatively low viscosity phase to insure thorough incorporation andsubsequent hardening of the resins to form a hard, tough coating on thesurfaces of the cell walls thus creating resistance to compression.

Several examples of the carbonaceous material used in this invention areshown in the following examples.

EXAMPLE 1 A quantity of ground cork was treated with urea-formaldehyderesin in the following manner. The cork, 354 lbs., was placed in a pandryer and heated to about 150-160 F. Meanwhile, a solution was preparedby dissolving 135 lbs. of urea in 402 lbs. of a 37% (by weight) aqueoussolution of formaldehyde. This solution was then sprayed on the hotcork, which was being constantly mixed by rotating plows, over a periodof about /2 hour. Heating was continued until the cork was dry and thetemperature had reached about 200 F., a period of about seven hours. Thecork was then discharged from the dryer and after cooling was ready foruse. The quantity of impregnated cork obtained'was 549 lbs. andcontained 38.3% of resin. The cork showed the following screen analysis:

Other properties of the cork before and after Per cent On 12 mesh 2 On20 mesh. 38 On 30 mesh 36 On 40 mesh -l l4 On meshf 4 Thorugh 60 mesh 6The treated cork feels crisp and hard in contrast to the softness of theordinary granulated cork. v

Five hundred parts by weight of ground cork was mixed with 700 parts byweight of 37% (by weight) formaldehyde solution to which 26 parts byweight of concentrated hydrochloric acid had been added to serve ascatalyst. Two hundred sixteen parts by weight of cresol was added andthe whole mixed together. The treated cork mixture was then dried andtheresin hardened by heating for seven hours in an oven at about 135 C.A yield of .706 parts by weight of treated cork containing 33% of resinwas obtained.

EXAMPLE 3 treated cork containing 36.5% of resin was obtained.

' EXAMPLE 4 Five hundred parts by weight of ground balsa wood was placedin a steam-jacketed kettle equipped with a stirring device. A solutionof 126 parts by weight of urea dissolved in 580 parts by we'ght of 37%(by weight) formalin solution was added to the balsa and the mixture wasstirred for half an hour. Then the kettle was heated for 4 hours withsteam to effect the resin reaction and to dry the mixture. The mixturewas finally heated with lb. steam for about two hours to complete thedrying and harden the resin. A yield of 665 parts by weight of balsa,

containing about 28.5% of resin, resulted.

Per cent On 12 mesh"-.. 1.0 On 20 mes 39.5 On 30 mes 20.5 On 40 mes 12.5Through 40 mesh 26.5

\ EXAMPLE 5 Fivehundred parts by weight of cork was mixed with 420 partsby weight of'a 60% solution of an alcohol-soluble urea-formaldehyderesin Formite F-224) and dried two hours in thin layers in an oven at C.A yield of seven hundred two parts by weight of treated cork containing33% ofresin was obtained.

Examine formaldehyde soltion was added with stirring to UntreatedTreated o. 09 1 0.19 5. Q 1. 2 cork so a Resin content -.per cent" 13823 ofdry weight. f

the bagasse.

Steam was applied to the jacket and the material was dried and the resinhardened during a period of 4 hours. About 693 parts by weight oftreated bagasse containing 31% of resin was obtained. a

Treated cork 3 Treated cork 7 L...

Chalk 1. 1. 0 l. 0

Density, gin/cc 1. $6 1. 41 Sensitivenoss:

Shot after 2: hrs. at y lbs/sq. in. 2 at 67 2 at 250 2 st 150Fivehundred parts by weight of cork was mixed with resolution of 125parts by weight of 20 cp. chlorinated rubber and 125 parts by weightescorts (100% gelatin mite, Table 4), and in extra geletins of 607;,Table 5. These selatlns were tested. fortweter-resistance by theprocedure given hereinbefore. The first gelatin in each table is a ofBakelite 3560 in 500 parts by Weight of toluene. formulated according tocommercial composi- The mixture was placed in an oven end dried for0118, but th hers 11mm 0111 treated low a. period or 2 hours at 135 c.About 720 parts density. cellular, carbon ceous m terial. Excmie byweight of treated curl: contoinind 34% of resin nation of these data.shows the very marked in was obtained. provement resulting from the useof the treated The carbonaceous materials described emve cerbonsceousmateriel.

Tonto 2 60% gelatin dymmites Nitroglyoorin Nitrocellulose. Sodiumnitrate Wood pulp Balso pulp Ivory meaL Wheat flour. Untreated cork.-Treated cork l l Treated cork 2 Treated balsa 4 Treated bagasso 5Treated bagasse 6 1.5!. 1.51 1.46 1.52 1.52 K 24atl50 24atl50 seem24atl60 21124120 24atl50 2at250 l The following list gives thecompositions ofthotreated carbonaceous materials:

, Treated cork l38.3% urea formaldehyde resin Treated cork 233% cresol(ormaldeh do resin Treated cork 3-36.47 thlourea lorma dohyde resinTreated balsa 4-28A o urea formaldehyde resin Treated bagssse 5-3l% ureaiormaldehyde resm Treated bagasso 6-35.6% urea formaldehyde resinTreated cork 7-347 resin consisting of equal parts of chlorinated rubberand a heat-hardening phenolic resin have been used to produce greatlyimproved gela- It will be noted that in the above table the tindynamites. The various dynamite compositreated material used givesactual materiel contions prepared by using the treated carbonaceousmaterials were tested for underwater use by placing three '2 x 16 sticksof the gelatin dynamite composition; end to end in a steel pip capped atthe lower end. A No. 6 or No. 8 electric blasting cap was inserted inthe first stick of gelatin dynamite and the pipe filled with water. Theblasting cop wires were'fastened to the terminalsof arsparkplug mountedin a pipe cap. This cap was screwed on to the pipe and the pressure inthe pipe was built up by applying compressed air through a valve. Anydesired pressure within reason may be obtained in this way. The pipe orbomb containing the gelatin under water pressure was allowed to standfor any desired period of time, and then laid horizontally on top of 5lead cylinders, 1 in. diameter and 2 in. high, each covered with a steeldisc of the same diameter. These five lead cylinders I were spaced atintervals i'under the pipe and the charge fired. If the charge shootscompletely, all

or the lead cylinders are compressed to a coa siderable degree, forexample, as much as an inch or more. If the detonation does not propcompletely, the cylinders under the portions of the charge which failwill not be compressed; in

lations, which give the results of its use in the socalled,L. F. (lowfreezing) gelatins (60% imd 80% strengths, Tables. 2 and 3), inblasting. gelatin gelatin TABLE 3 L. F. gelatins Nitrogl oerin e1. 0' o.o N itr ulose. 2. 6 12. 5 18. 5 1s. 5 2. 0 2. 0 4. 0 4. 0 l. 5 1. 5 l. 5-1. 5 1. 0 1. 0 Untreated mr 2. 0 Treated cork 1.. c 2.0

x 100.0 100.0 Sensltivenoss: Shot after hrs. at I lbs/sq. in..

pressure"; 2 at $3 2 at q TABLE 4 Blasting gelatin Niirogl oerin 89.0at. Nitrooe ulose 6.0 6. Balsa 4. 0 Treated cork 1--.. 4. Chalk 1. 0 1.

Sensitivoneasz, Shot aims hrs. at y lbs/sq. in.

pressure I 2 at 43' 2 at 87 tent, exclusive of resin, 01- about 2%,except in Example G where net corkcontent is about 1.25%.

Nitroglycerin TABLE 60% ammonium nitrate gelatin Nitrocellulose Sodiumnitrate fur Untreated cork Treated cork 1 2. 0

D enslty, gut/cc Sensitiveness: Shot after 1' hrs. at 1,!

lbs/sq. in

In order to show the decrease in compressibility of the gelatindynamites containing the treated carbonaceous materials, the followingtest was conducted. A section of gelatin dynamite 2 inches in diameterand 2 inches long was placed under kerosene, or other suitable liquid,and the volume thereof determined. The liquid was then subjected topressure, for example, 75 lbs/sq. in. gauge for minutes, and the volumeof the sample observed. The theoretical reduction of the gelatins volumewhich should result from the above pressure was then calculated from thetheoretical maximum density and its actual bulk density. The actualcompressibility of the gelatin was then erpressed as a relativecompressibility? i. e., the ratio of the observed decrease in volume tothe theoretical decrease. The results on a number of gelatin samplescontaining treated cork are given in Table 6 which show that therelative compressibility decreases as the ability to shoot underpressure improves.

Cork l-33.8%resin consisting of chlorinated rubber and 50% phenolicaldehyde resin.

Cork 2-32.7%urea-forrnaldehyde resin.

Cork 339.6%-urea-iormaldehyde resin.

1 Each gelatin contains a quantity of'treated cork equivalent to 2%actual cork.

In the above formulations where the use of nitroglycerin is indicated,it should be understood that by the term nitroglycerin is meant eitherthis compound by itself or with the addition or partial substitution ofany of the commonly used freezing point depressants such, for example,as ethylene glycol dinitrate, nitrated polymerized glycerin, nitratedsugars, nitrated chlorhydrins, etc. 'The term nitroglycerin as heredescribed is well accepted-in the explosive art.

The explosive. compositions of our invention have been found especiallyadvantageous in blasting operation where there is a substantial liquidhead above the explosive charge. In dee well blasting such as, forexample, seismograph pros pecting, quarrying and oil well shooting,/these compositions have proved invaluable since their sensitiveness isnot impaired under the high'pressures encountered. The compositions havealso found use in underwater operations, such as are carried out inchannels and harbors, due to their constant sensitivity.

It will be understood that the details and examples hereinbefore setforth are illustrative only, and that the invention as broadly describedand claimed is in no way limited thereby.

What we claim and desire to protect by Letters Patent is:

1. A gelatin type explosive composition which includes as ingredientsnitroglycerin and a cellular, carbonaceous material selected from thegroup consisting of cork, balsa, bagass, bongo wood and hemp hurds andtreated with a synthetic resin heat-hardened in situ, said treatedcarbonaceous material characterized by having stifiened cell walls andby having substantially the same-nitroglycerin absorbency as the untreated material.

2. A gelatin type explosive composition comprising a stiffened,cellular, carbonaceous mate-- rial selected from the group consisting ofcork,

balsa, bagasse, bongo wood and hemp hurds, said material treated with asynthetic resin heat hardened in situ, and characterized by anitroglycerin absorbency substantially equal to the absorbency of theuntreated material and said composition containing less than aboutnitroglycerin, said composition characterized by a density greater than1.4 grams per cc., and the ability to detonate after 2 hours at 200 lbs.8. sq. inch water pressure when disposed in a 2 x 48 inch column.

3. A gelatin type explosive composition com prising a stiffened,cellular, carbonaceous material selected from the group consisting ofcork, balsa, bagasse, bongo wood and hemp hurds, said material treatedwith a synthetic resin heat: hardened in situ, and characterized by anitroglycerin absorbency substantially equal to the absorbency of theuntreated material and said composition containing between about 40 andabout 60% nitroglycerin said composition characterized by a densitygreater than 1.4 grams per cc., and the ability to detonate after twohours under 200 lbs. per sq. inch water pressure when disposed in a 2 x48 inch column.

4. An ammonium nitrate gelatin dynamite composition comprising astiifened, cellular, carbonaceous material selected from the groupconsisting of cork, balsa, bagasse, bondo wood and hemp hurds, saidmaterial treated with a synthetic resin heat-hardened in situ,and-charac- .terized by a. nitroglycerin absorbency substantially equalto the absorbency of the untreated material and said compositioncontaining less thanabout 40% nitroglycerin said compositioncharacterized by a density greater than 1.5 grams per cc., and theability to detonate after 2 hours at lbs.'per sq. inch water pressurewhen disposed in a 2 x 48 inch column.

5. A gelatin type explosive composition com prising a liquid explosive,nitrocellulose, and between about 1.25% and about 4.0% of 9. treatedcellular carbonaceous material selected from the group consisting ofcork, balsa, bagasse, bongo wood and hemp hurds, having the cell wallsthereof stiffened with a synthetic resin heat hardened in situ, saidresin comprising between about 15% and about 45% by weight of saidmaterial.

6. A gelatin type explosive composition comprising a liquid explosive,nitrocellulose, and between about 1.25% and about 4.0% of a treatedcork. having the cell walls thereof stiffened with said resin comprisingbetween about 15% and about 45% by weight of said material. 7

'7 A gelatin type explosive composition comprising a liquid explosive,nitrocelluloseand between about 1.25%and about 4.0% of treated ing the'cell walls thereof stifiened with a phenol aldehyde resin heat hardenedin situ, said resin comprising between about 15% and about 45% .byweight of said material.

9. A gelatin type explosive composition comprising a liquid explosive,nitrocellulose, and be tween'about 1.25% and about 4.0% or a hay 9 aphenol aldehyde resin heat hardened in situ.

ing the cell walls thereof stiflened with a urea aldehyde resin heathardened in situ, said resin comprising between about 15% and about 45%by weight of said material.

10. A gelatin'type explosive, composition comprising a liquid explosive,nitrocellulose, and between about 1.25% and about 4.0%-0! bagasse havingthe cell .walls thereof stifiened with a phenol aldehyde resin heathardened in situ, said resin comprising between about 15% and about 45%by weight of said material.

11. A gelatin type explosive composition comprising a liquid explosive,nitrocellulose, and between about 1.25% and about 4.0% 'of bagassehaving the cell walls thereof stifiened with a urea aldehyde resin heathardened in situ, said resin comprising between about 15% and about 45%by weight of said material.

1 CHARLES D. HITTING.

ROBMT W. LAWRENCE.

